Kinetic Particle Theory

• Neutron


  Represents one neutron
• Proton


  Represents one proton
• Mass number


  Total number of protons and neutrons in the nucleus of an atom
• Electron


  Represents one electron
• Atoms are electrically neutral
• Proton number/Atomic number


  The number of protons in an atom
• Mass (nucleon) number


  The total number of protons and neutrons in the nucleus of an atom
• Atoms of metals lose electrons to form positively charged ions (cations)
• Atoms of non-metals gain electrons to form negatively charged ions (anions)
• Ion


  The particle formed when an atom gains or loses electrons
• Sodium atom


  • Has 1 electron in the valence (outermost) shell
• Electronic structure of an atom

  • First shell can hold up to 2 electrons
  • Second and third shell can hold up to 8 electrons
• The number of shells indicates the period number in the Periodic Table
• Isotopes


  Atoms of the same element with the same number of protons but different number of neutrons
• Properties of isotopes


  • Undergo the same types of chemical reactions
  • May have different physical properties
• Chemical reactions involve only the electrons
• Different number of neutrons = different relative atomic masses
• Atoms with the same number of valence electrons are found in the same group in the Periodic Table
• Valence electrons determine the chemical properties of an element
• Atoms are the smallest particles that have the chemical characteristics of an element
• The nucleus contains protons and neutrons
• Electrons are found in shells around the nucleus
• The number of protons equals the number of electrons in a neutral atom
• Atoms are electrically neutral because the number of positive charges (protons) balances the number of negative charges (electrons)
• Calcium atom loses 2 electrons to form Ca2+ ion
• Fluorine atom gains 1 electron to form F- ion